The scaphoid bone in the human wrist is the largest bone of the proximal row of the carpus on the lateral (radial) side, articulating with the radius, lunate, capitate, trapezium, and trapezoid. The scaphoid is surrounded on 80% of its surface by joint fluid containing fibrinolysin, a substance that dissolves blood clots. Because blood clots are necessary for the healing of bone fractures, the substantial presence of fibrinolysin around the scaphoid inhibits healing of a fracture of that bone unless the fracture fragments are fixed in sufficiently good apposition that joint fluid is prevented from entering the fracture site. Failure to properly fix the bone fragments into apposition will result in a non-union because of the presence in the fracture site of joint fluid.
In addition to an undesirable non-union, resulting from poor apposition, a fracture of the scaphoid through its waist often leads to avascular necrosis or death of the distal pole of the bone. This is because the blood supply to the bone is chiefly through the proximal pole and an unhealed fracture at the bone waist cuts off the blood supply to the distal pole, resulting eventually in severe arthritis and deformity of the wrist.
The traditional conservative treatment of a fractured scaphoid includes the application of a cast to the hand and thumb with the hand in radial deviation in an effort to oppose the fracture ends of the bone. Surgical intervention to fix the scaphoid bone typically includes the use of a Herbert screw that requires the expertise of a hand surgeon specialist and results in an extended exposure of the scaphoid bone.
The percutaneous method used with the fixation device of the present invention allows a less experienced hand surgeon or an orthopedist to fix a scaphoid fracture with a screw without the surgical procedures of the past. Such simplification further leads to effectual apposition of the bone fragments and an overall improved result, including the minimization of surgical exposure of the wrist with the attendant increased risk of infection and limitation of wrist movement.
The apparatus of the present invention is an improvement to the fixation and clamping apparatus disclosed in U.S. Pat. No. 6,695,841.